U.S. patent application number 11/867047 was filed with the patent office on 2008-04-10 for optical communication lens and tube body constituting optical element module.
This patent application is currently assigned to YAZAKI CORPORATION. Invention is credited to Hisao MATSUKURA, Motonori MIYANARI, Naoshi SERIZAWA.
Application Number | 20080085077 11/867047 |
Document ID | / |
Family ID | 39111499 |
Filed Date | 2008-04-10 |
United States Patent
Application |
20080085077 |
Kind Code |
A1 |
MIYANARI; Motonori ; et
al. |
April 10, 2008 |
OPTICAL COMMUNICATION LENS AND TUBE BODY CONSTITUTING OPTICAL
ELEMENT MODULE
Abstract
An optical communication lens arranged between an optical
element and an optical fiber terminal includes a first lens part
having an aspherical convex shape facing the optical element, a
second lens part having an aspherical convex shape facing the
optical fiber terminal, and an intermediate part integrally formed
with the first lens part and the second lens part therebetween. The
first lens part, the second lens part and the intermediate part are
integrally formed and are comprised of a resin having optical
transparency. Shapes of the first lens part and the second lens
part are asymmetric to each other. The second lens part is thicker
than the first lens part.
Inventors: |
MIYANARI; Motonori;
(Susono-shi, JP) ; SERIZAWA; Naoshi; (Susono-shi,
JP) ; MATSUKURA; Hisao; (Ageo-shi, JP) |
Correspondence
Address: |
SUGHRUE-265550
2100 PENNSYLVANIA AVE. NW
WASHINGTON
DC
20037-3213
US
|
Assignee: |
YAZAKI CORPORATION
Tokyo
JP
|
Family ID: |
39111499 |
Appl. No.: |
11/867047 |
Filed: |
October 4, 2007 |
Current U.S.
Class: |
385/35 |
Current CPC
Class: |
H01L 2224/48091
20130101; G02B 6/4206 20130101; H01L 2224/48137 20130101; H01L
2924/00014 20130101; H01L 2224/48091 20130101 |
Class at
Publication: |
385/35 |
International
Class: |
G02B 6/32 20060101
G02B006/32 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2006 |
JP |
2006-272534 |
Claims
1. An optical communication lens arranged between an optical
element and an optical fiber terminal, comprising: a first lens
part having an aspherical convex shape facing the optical element;
a second lens part having an aspherical convex shape facing the
optical fiber terminal; and an intermediate part integrally formed
with the first lens part and the second lens part therebetween,
wherein the first lens part, the second lens part and the
intermediate part are integrally formed and are comprised of a
resin having optical transparency; wherein shapes of the first lens
part and the second lens part are asymmetric to each other: and
wherein the second lens part is thicker than the first lens
part.
2. The optical communication lens according to claim 1, wherein the
optical element is a light emitting element; and wherein the first
lens part is formed into a shape that when a light from the light
emitting element passes through from the first lens part to the
second lens part, the light propagating through the intermediate
part is extended in a direction of propagation.
3. The optical communication lens according to claim 1, wherein the
optical element is a light receiving element; and wherein the
second lens part is formed into a shape that when a light from the
optical fiber terminal passes through from the second lens part to
the first lens part, the light propagating through the intermediate
part is narrowed in a direction of propagation.
4. The optical communication lens according to claim 1, wherein the
optical element is Vertical Cavity Surface Emitting Laser (VCSEL)
or Photo Diode (PD); and wherein the optical fiber is Polymer Clad
Fiber (PCF).
5. A tube body for a optical device module having an optical
element, comprising: a cylindrical tube part for containing an
optical fiber terminal or a ferrule mounted on the optical fiber
terminal; and an optical communication lens to be arranged between
the optical element and the optical fiber terminal, wherein the
optical communication lens includes: a first lens part having an
aspherical convex shape facing the optical element; a second lens
part having an aspherical convex shape facing the optical fiber
terminal; and an intermediate part integrally formed with the first
lens part and the second lens part therebetween, wherein the
optical communication lens is comprised of a resin having optical
transparency; wherein shapes of the first lens part and the second
lens part are asymmetric to each other; wherein the second lens
part is thicker than the first lens part; and wherein the optical
communication lens is integrally formed with the cylindrical tube
part therein.
Description
BACKGROUND
[0001] The present invention relates to an optical communication
lens interposed between a light emitting element or a light
receiving element and an optical fiber terminal and a tube body of
an optical element module using the optical communication lens.
[0002] As a related art optical element module, one disclosed for
example in JP-A-2006-30813 is known. In FIG. 7, an optical element
module 1 includes a light emitting device 2 and an enclosure 3. The
optical element module 1 shown in FIG. 7 serves as a light emitting
side in optical communications. The light emitting device 2
includes a substrate 4, a light emitting element 5 and an
electronic component 6 mounted on the front surface of the
substrate 4, and a sealing resin 7 for sealing the light emitting
element 5 and the electronic component 6. The enclosure 3 includes
a main body 8 and a tube body 9 for inserting optical fibers to be
integrated with the main body 8 and is formed into an illustrated
shape.
[0003] At the rear part of the substrate 4 of the light emitting
device 2 are formed a plurality of latching concave parts 10. In
the concave parts 10 are engaged latching hook parts 11 formed on
the main body 8 of the enclosure 3. The light emitting device 2 is
housed in contact with a stepped part 12 inside the main body 8.
The light emitting device 2 is prevented from dropping by way of
the fitting engagement of the concave parts 10 and the hook parts
11.
[0004] In this arrangement, when the light emitting device 2 is
fitted into the main body 8, the light emitting element 5 is
exposed through the sealing resin 7 from the opening at the tip of
the tube body 9 of the enclosure 3. When an optical fiber terminal
is inserted into the tube body 9, the inserted optical fiber
terminal is opposed to the light emitting element 5. While not
illustrated, the optical fiber terminal has a ferrule mounted
thereon having an outer diameter matching the inner diameter of the
tube body 9.
[0005] In the related art, the ferrule mounted on the optical fiber
terminal is inserted into the tube body 9 so that the inner
diameter of the tube body 9 has a dimension slightly larger than
the outer diameter of the ferrule. Thus, the ferrule may be axially
misaligned in the direction of an arrow P shown in FIG. 7 by a
difference in dimension from the tube body 9. This presents a
problem that an optical signal from the light emitting element 5 is
not adequately coupled to the optical fiber exposed from the end
surface of the ferrule. In other words, the related art includes an
element that degrades the coupling efficiency. Further, an optical
signal from the light emitting element 5 cannot be adequately
connected in case the ferrule is inserted to a shallow depth into
the tube body 9, that is, to a shallow depth in the direction of
the arrow Q shown in FIG. 7.
[0006] In recent years, the increasing amount of information
transfer volume and growing needs for real-time processing require
a higher transmission speed of an optical signal. Reducing the
light receiving area of an optical fiber is needed to attain a
higher transmission speed. The problem is that a reduced light
receiving area of an optical fiber may not be supported by the
optical element module 1 with lower coupling efficiency.
SUMMARY
[0007] The invention has been accomplished in view of the above
circumstances. An object of the invention is to provide an optical
communication lens capable of enhancing the optical coupling
efficiency and a tube body of an optical element module using the
optical communication lens.
[0008] In order to solve the problem, the invention provides An
optical communication lens arranged between an optical element and
an optical fiber terminal, comprising:
[0009] a first lens part having an aspherical convex shape facing
the optical element;
[0010] a second lens part having an aspherical convex shape facing
the optical fiber terminal; and
[0011] an intermediate part integrally formed with the first lens
part and the second lens part therebetween,
[0012] wherein the first lens part, the second lens part and the
intermediate part are integrally formed and are composed of a resin
having optical transparency;
[0013] wherein shapes of the first lens part and the second lens
part are asymmetric to each other; and
[0014] wherein the second lens part is thicker than the first lens
part.
[0015] Preferably, the optical element is a light emitting element,
and the first lens part is formed into a shape that when a light
from the light emitting element passes through from the first lens
part to the second lens part, the light propagating through the
intermediate part is extended in a direction of propagation.
[0016] Preferably, the optical element is a light receiving
element, and the second lens part is formed into a shape that when
a light from the optical fiber terminal passes through from the
second lens part to the first lens part, the light propagating
through the intermediate part is narrowed in a direction of
propagation.
[0017] With the invention having such a characteristic, it is
possible to arrange a lens having a desired aberration between a
light emitting element or a light receiving element (an optical
element) and an optical fiber terminal. An optical communication
lens of the invention is formed into the shape according to the
invention and has an aberration so that it ensures high coupling
efficiency even in the presence of slight misalignment of the light
emitting element or light receiving element and the optical fiber
terminal. Introduction of an aberration provides a focus as a
circle having an area rather than a single point at a focal point.
The invention thus ensures high coupling efficiency. With the
optical communication lens of the invention, providing an
aberration in the shape according to the invention obtains a spot
diameter ample enough in terms of coupling even when the optical
fiber terminal is brought near or placed away from the inventive
optical communication lens. High coupling efficiency is provided in
this case also.
[0018] Preferably, the optical element is Vertical Cavity Surface
Emitting Laser (VCSEL) or Photo Diode (PD), and the optical fiber
is Polymer Clad Fiber (PCF).
[0019] With the invention having such a characteristic, as
understood from the first aspect of the invention, an optical
communication lens having high coupling efficiency is provided. The
optical communication lens includes a light emitting element or a
light receiving element using a VCSEL (laser diode) or a PD (photo
diode) and an optical fiber using a PCF (Polymer Clad Fiber). This
ensures a higher transmission speed.
[0020] In order to solve the problem, the invention provides a tube
body for a optical device module having an optical element,
comprising:
[0021] a cylindrical tube part for containing an optical fiber
terminal or a ferrule mounted on the optical fiber terminal:
and
[0022] an optical communication lens to be arranged between the
optical element and the optical fiber terminal,
[0023] wherein the optical communication lens includes: [0024] a
first lens part having an aspherical convex shape facing the
optical element; [0025] a second lens part having an aspherical
convex shape facing the optical fiber terminal; and [0026] an
intermediate part integrally formed with the first lens part and
the second lens part therebetween,
[0027] wherein the optical communication lens is comprised of a
resin having optical transparency;
[0028] wherein shapes of the first lens part and the second lens
part are asymmetric to each other;
[0029] wherein the second lens part is thicker than the first lens
part; and
[0030] wherein the optical communication lens is integrally formed
with the cylindrical tube part therein.
[0031] With the invention having such a characteristic, it is
possible to provide an optical element module with high coupling
efficiency. The configuration of the optical element module will be
described under Best Mode for Carrying Out the Invention.
[0032] The invention offers an advantage that optical coupling
efficiency is enhanced. The invention offers an advantage that the
transmission speed is increased. The invention offers an advantage
that an optical element module with high coupling efficiency is
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above objects and advantages of the present invention
will become more apparent by describing in detail preferred
exemplary embodiments thereof with reference to accompanying
drawings, wherein like reference numerals designate like or
corresponding parts throughout the several views, and wherein:
[0034] FIG. 1a is a cross-sectional view of an embodiment of an
optical element module according to the invention;
[0035] FIG. 1b is a cross-sectional view of an optical
communication lens according to the invention;
[0036] FIG. 2 is a perspective view of the optical element
module;
[0037] FIG. 3 is an exploded perspective view of the optical
element module;
[0038] FIG. 4 is a front view of the optical element module in the
sub-assembly state;
[0039] FIG. 5 is a cross-sectional view of the optical element
module in the sub-assembly state;
[0040] FIG. 6 is an explanation drawing related to the coupling
efficiency by the optical communication lens; and
[0041] FIG. 7 is a cross-sectional view of a related art optical
element module.
DETAILED DESCRIPTION
[0042] Referring to FIG. 1, an optical connector 21 used for
optical communications includes an optical element module 22, an
optical connector housing 23 made of a synthetic resin, and a
housing cap 24 made of a synthetic resin. The optical element
module 22 includes an optical communication lens 45 according to
the invention.
[0043] The optical connector 21 in this embodiment is one mounted
on a vehicle although the invention is not limited thereto. The
optical connector 21 in this embodiment uses two optical element
modules 22 according to the invention arranged side by side in the
optical connector housing 23 for bidirectional optical
communications although the invention is not limited thereto.
Another optical element module is arranged at the back of the
optical element modules 22 shown in FIG. 1. A configuration
dedicated to transmission or reception may be made. The component
members of the optical connector 21 will be described referring to
FIGS. 1 through 5.
[0044] The optical element module 22 includes a light emitting
element 25 (or light receiving element) (an optical element), a
lead frame 26, a resin enclosure 27, a resin tube body 28, a
silicone resin sealing part 29, an IC 30 and an electronic
component 31.
[0045] The light emitting element 25 is mounted on the lead frame
26 together With the IC 30 and the electronic component 31. An
optical signal output from the light emitting element 25 is
generated by converting an electric signal. As the light emitting
element 25, an LED or a VCSEL is generally known. In this example,
a VCSEL is used to enhance the transmission speed. The light
emitting element 25 is mounted on a small substrate 32 arranged on
the lead frame 26.
[0046] The lead frame 26 is formed into an illustrated shape by
blanking a conductive thin metallic plate, The lead frame 26 is not
separated from a carrier formed via blanking until insert forming
described later takes place or the light emitting element 25 is
mounted.
[0047] The lead frame 26 has a through hole 33 formed on the center
axis, for example. The through hole 33 is formed to penetrate the
lead frame 26 in a diameter slightly larger than the diameter of an
ejector pin described later. In close proximity to the through hole
33 is set an element mounting part 34 for the light emitting
element 25. The element mounting part 34 is set in the size of the
substrate 32. In close proximity to the element mounting part 34
are mounted the IC 30 and the electronic component 31.
[0048] An enclosure 27 is formed through resin molding where the
lead frame 26 is inserted into a predetermined position. The
enclosure 27 is formed into a rectangular shape having an opening
at the front and including a shallow bottom. To be more precise,
the enclosure 27 is formed to include a rear bottom wall 35, an
upper wall 36, a lower wall 37, a left wall 38, a right wall 39 and
an opening 40. The opening 40 is formed as a part opened by the
ends of the upper wall 36, the lower wall 37, the left wall 38 and
the right wall 39. The ends of the upper wall 36, the lower wall
37, the left wall 38 and the right wall 39 are formed to be
continuous in a flat plane. In such a flat plane is formed a
concave part 41.
[0049] The concave part 41 is formed into a groove-shaped part that
has a rectangular shape when the enclosure 27 is viewed from the
front as shown in FIG. 4. The concave part 41 is formed outside the
opening 40. The concave part 41 is formed as a non-locking uneven
part on the enclosure 27. The cross-sectional shape of the concave
part 41 is not limited to a rectangle or a square but may be a
character of V or U. The shape of the concave part 41 is not
particularly limited as long as the tube body 28 can be slightly
moved for alignment with a non-locking uneven part (described
later) on the tube body 28 inserted. To the concave part 41 is
applied a fixing adhesive in the assembly process of the optical
element module 22.
[0050] The enclosure 27 includes a marker 42 serving as a reference
for positioning and used for viewing or image processing. The
marker 42 is formed on the rear bottom wall 35 when the lead frame
26 is insert-molded into a predetermined position. To be more
precise, the marker 42 is formed when the enclosure 27 is
resin-molded. That is, the marker 42 is formed using the marks of
the ejector pin of the forming mold. The marker 42 is formed in a
position exposed from the through hole 33 of the lead frame 26. The
marker 42 is formed by penetrating the ejector pin of the forming
mold into the through hole 33 of the lead frame 26 in resin molding
of the enclosure 27.
[0051] The tube body 28 is formed through resin molding that uses a
resin material having optical transparency. The tube body 28
includes a lid part 43, a tube part 44 and an optical communication
lens 45 of the invention. The lid part 43, the tube part 44 and the
optical communication lens 45 are formed integrally. The tube body
28 is formed of a single component including the lid part 43, the
tube part 44 and the optical communication lens 45.
[0052] The lid part 43 is formed into a rectangular shape that can
cover the opening 40 of the enclosure 27. On the lid part 43 is
formed a convex part 46 for fixing via an adhesive at a position on
a flat surface of each end of the upper wall 36, lower wall 37,
left wall 38 and the right wall 39 of the enclosure 27. The convex
part 46 is formed as a non-locking uneven part on the lid part 43.
The convex part 46 is formed to the shape and arrangement of the
concave part 41 of the enclosure 27.
[0053] The convex part 46 may be formed on the enclosure 27 and the
concave part 41 may be formed on the lid part 43. The convex part
46 and the concave part 41 are formed in shapes to allow insertion
and so that both parts are not engaged to each other. The convex
part 46 and the concave part 41 are not designed to fix the tube
body 28 and the enclosure 27. Fixing is basically made using an
adhesive or equivalent means. The convex part 46 and the concave
part 41 have dimensions so that a minute backlash (gap), that is, a
backlash necessary for positioning described later will be provided
when the convex part 46 is inserted into the concave part 41.
[0054] The tube part 44 is formed as a part into which the terminal
of an optical fiber is inserted via a ferrule, or the terminal of
an optical fiber is inserted directly. The tube part 44 is formed
into a cylindrical shape. Inside the tube part 44 is integrated an
optical communication lens 45 (or an optical communication lens 45
may be separately formed). The optical communication lens 45 is
arranged in close proximity to the continuous part between the tube
part 44 and the lid part 43 in this embodiment.
[0055] The optical communication lens 45 is arranged to be
interposed between the terminal of an optical fiber and a light
emitting element 25. The optical communication lens 45 is arranged
considering the distance to the optical fiber terminal and the
distance to the light emitting element 25. The optical
communication lens 45 is formed to be convex on the surface facing
the optical fiber terminal and on the surface facing the light
emitting element 25. The optical communication lens 45 is formed so
that both convex surfaces are aspherical.
[0056] As an optical fiber, a POF or a PCF is generally known. In
this example, a PCF is used to enhance the transmission speed.
[0057] The optical communication lens 45 will be further detailed.
The optical communication lens 45 is formed to include: a first
aspherical convex lens part 45a (a first lens part) formed into an
aspherical shape and convex on the surface facing the light
emitting element 25, a second aspherical convex lens part 45b (a
second lens part) formed into an aspherical shape and convex on the
surface facing the optical fiber terminal, and an intermediate part
45c arranged between the first aspherical convex lens part 45a and
the second aspherical convex lens part 45b and continuous thereto.
The optical communication lens 45 are formed so that the first
aspherical convex lens part 45a and the second aspherical convex
lens part 45b are formed into asymmetric shapes.
[0058] Talking of the asymmetric shapes, assuming that the lens
diameter is the same, thickness T2 of the second aspherical convex
lens part 45b is greater than thickness T1 of the first aspherical
convex lens part 45a (see FIG. 1b). The asymmetric shapes are
formed so that light propagated through the intermediate part 45c
will be extended (or narrowed in the case of a light receiving
element) in the direction of propagation.
[0059] The optical communication lens 45 formed into the above
shape generates a desired aberration between the light emitting
element 25 and the optical fiber terminal. The optical
communication lens 45 in the above shape and providing an
aberration assures high coupling efficiency despite slight
misalignment of the light emitting element 25 and the optical fiber
terminal. That is, introduction of an aberration into the optical
communication lens 45 provides a focus as a circle having an area
rather than a single point at a focal point. This ensures high
coupling efficiency (described later referring to FIG. 6).
[0060] The optical communication lens 45 formed into the above
shape obtains a sufficient spot diameter with respect to the
coupling even when the optical fiber terminal is brought near or
placed away from the optical communication lens 45. This ensures
high coupling efficiency in this case also (described later
referring to FIG. 6).
[0061] A silicone resin sealing part 29 is formed into an
illustrated state by potting a silicone resin for sealing into the
enclosure 27. The light emitting element 25, the IC 30 and the
electronic component 31 mounted on the lead frame 26 are protected
by the silicone resin sealing part 29. In this embodiment, the
silicone resin sealing part 29 is formed so that its apex surface
will be slightly lower than the opening 40.
[0062] In a space formed between the apex surface of the silicone
resin sealing part 29 and the opening 40 with the tube body 28
mounted on the enclosure 27 exists air, which exits outside via a
minute backlash between the convex part 46 and the concave part 41.
In this embodiment, a non-fixed part is formed where an adhesive is
not applied, where air moves toward the inside and outside.
[0063] Next, assembly of the optical element module 22 will be
described based on the above configuration.
[0064] The lead frame 26 with a carrier attached (otherwise the
lead frame 26 could break up) is set into a forming mold. Starting
resin molding of the enclosure 27 in this state forms the enclosure
27 with part of the lead frame 26 insert-molded. On the enclosure
27 is formed a positioning marker 42 using the marks of an ejector
pin of the forming mold (refer to FIG. 4). The ejector pin is
arranged on the mold body with the dimensional precision of the
forming mold. Thus, with such an ejector pin, the marker 42 is
arranged with high precision.
[0065] In formation of the marker 42, the ejector pin penetrates
the through hole 33 of the lead frame 26. When the enclosure 27 is
resin-molded while the lead frame 26 is being inserted, the lead
frame 26 is prevented from being moved by the flow of resin. This
completes molding of the enclosure 27 and positioning of the lead
frame 26 with high precision.
[0066] When the opening 40 is exposed after the enclosure 27 is
resin-molded, part of the lead frame 26 is exposed. On the exposed
part, the light emitting element 25, the IC 30 and the electronic
component 31 are mounted and wiring is made. The light emitting
element 25 and the like are mounted using the marker 42 as a
positioning reference. Use of the marker 42 allows the light
emitting element 25 to be arranged with high precision with respect
to the lead frame 26 and the enclosure 27.
[0067] Next, potting of a silicone resin for sealing is made to the
enclosure 27. This process forms a silicone resin sealing part 29
in the enclosure 27. The light emitting element 25, the IC 30 and
the electronic component 31 mounted on the lead frame 26 are
protected by the silicone resin sealing part 29. When the light
emitting element 25, the IC 30 and the electronic component 31
mounted on the lead frame 28 are protected by the silicone resin
sealing part 29 and the lead frame 26 is detached from the carrier,
a sub-assembly as a state before the tube body 28 is fixed is
formed as shown in FIGS. 4 and 5.
[0068] Next, the tube body 28 is fixed to the enclosure 27 by using
an adhesive. This work includes a temporary fixing step of applying
an adhesive to the concave part 41 of the enclosure 27 and
inserting the convex part 46 of the tube body 28 therein, and
determining the fixing position of the tube body 28 while using the
light emitting element 25 as a positioning reference, and a final
fixing step of letting the adhesive harden that is applied to the
concave part 41 and completely fixing the tube body 28 to the
enclosure 27.
[0069] In this embodiment, the adhesive used is for example a
thermo-setting epoxy adhesive. The adhesive is applied to the
concave part 41 for example on the upper wall 36 and the lower wall
37 of the enclosure 27, and completely secures the tube body 28
onto the enclosure 27 when it hardens with heat treatment (for
example, for one hour at 100.degree. C.) after the temporary fixing
step.
[0070] In the temporary fixing step, when the tube body 28 is
minutely moved to determine the fixing position by using the light
emitting element 25 as a reference, each of the left wall 38 and
the right wall 39 of the enclosure 27 and the lid part 43 of the
tube body 28 are partially fixed to each other with an instant
adhesive (a cyanoacrylate instant adhesive having a UV bonding
feature). Partial fixing may be made through laser-based welding.
This maintains the enclosure 27 and the tube body 28 in stable
position without dislocating from each other while a thermo-setting
epoxy adhesive is hardening. Once the thermo-setting epoxy adhesive
hardens, the tube body 28 is fixed to the enclosure 27 with the
center axis of the tube part 44 aligned with the light emitting
element 25.
[0071] When the thermo-setting epoxy adhesive hardens and the tube
body 28 is completely secured to the enclosure 27, assembly of the
optical element module 22 is complete.
[0072] An optical connector housing 23 constituting the optical
connector 21 is formed into a shape with its front surface and rear
surface open respectively as illustrated. The opening on the front
surface is formed as a connector fitting part 47 into which a
counterpart optical connector is fitted. The opening on the rear
surface is formed as a module receiving part 48 for receiving the
optical element module 22. Between the connector fitting part 47
and the module receiving part 48 is formed a partition wall 49. A
through hole 50 is formed in the partition wall 49. The through
hole 60 is formed into a stepped shape so that the tube part 44 of
the optical element module 22 will be inserted and the lid part 43
will be abutted on the stepped part when the optical element module
22 is received in the module receiving part 48.
[0073] The optical connector housing 23 is formed so that the tube
part 44 will protrude into the connector fitting part 47 when the
optical element module 22 is received in the module receiving part
48. When the tube part 44 protrudes into the connector fitting part
47, the ferrule of the counterpart optical connector is inserted
into the tube part 44 and guided into position when optical
connectors are fitted into each other.
[0074] A housing cap 24 includes a locking projection 52 engaged to
a locking concave part 51 formed on the module receiving part 48 of
the optical connector housing 23. The housing cap 24 includes a
plurality of pressing parts 53 for pressing the optical element
module 22 against the partition wall 49 of the optical connector
housing 23 while locked to the module receiving part 48.
[0075] When the optical element module 22 is received in the module
receiving part 48 and the housing cap 24 is locked to the module
receiving part 48, assembly of the optical connector 21 is
complete. The optical element module 22 is fixed without a
backlash.
[0076] When assembly of the optical connector 21 is complete, the
optical connector 21 is fixed to the surface of a substrate. The
lead frame 26 of the optical element module 22 penetrates the
through hole of the substrate and is soldered to the rear surface
of the substrate. Part of the lead frame 26 may be bent and mounted
on the substrate. A numeral 54 represents a substrate fixing part
formed on the optical housing 23. The substrate fixing part 54 is
inserted into the substrate and is fixed thereto.
[0077] Next, the coupling efficiency by the optical communication
lens 45 will be described referring to FIG. 6. FIG. 6 is an
explanatory drawing concerning the coupling efficiency. Explanation
is made on the result of evaluation assuming that the diameter of
the optical fiber is 200 .mu.m.
[0078] Referring to FIG. 6, light (an optical signal) 55 from a
light emitting element 25 is propagated through the optical
communication lens 45 having an asymmetric shape including a first
aspherical convex lens part 45a and a second aspherical convex lens
part 45b. The diffused light 55 from the light emitting element 25
enters in the first aspherical convex lens part 45a and is
propagated inside an intermediate part 45c in an extended fashion
in the direction of propagation. The light 55 is emitted from the
second aspherical convex lens part 45b and is condensed toward a
focal point. The optical communication lens 45 with the desired
aberration described above obtained with this shape provides a spot
diameter of 42 micrometers at the focal point, a sufficient value
with respect to an optical fiber having a diameter of 200
micrometers. According to this result, the spot diameter obtained
is within some 120 micrometers even when the terminal of the
optical fiber is brought near or placed away from the optical
communication lens 45, or is dislocated by .+-.320 micrometers with
respect to the focal point. The optical communication lens 45 thus
offers good coupling efficiency.
[0079] As a comparison example of the optical communication lens
45, assume, while not shown, a lens of a symmetric shape using the
first aspherical convex lens part 45a in each side (the optical
communication lens 45 with the second aspherical convex lens part
45b replaced with the first aspherical convex lens part 45a). In
the above evaluation method, a spot diameter of 230 micrometers at
the focal point is obtained. This is not a spot diameter sufficient
for the optical fiber having a diameter of 200 micrometers. The
coupling efficiency in this example is about 90 percent. The spot
diameter obtained is some 290 micrometers when the optical fiber
terminal is brought near or placed away from the optical
communication lens. A sufficient spot diameter is not obtained in
this case either (the corresponding coupling efficiency is as low
as about 60 percent).
[0080] As described referring to FIGS. 1 through 6, the invention
provides an advantage that optical coupling efficiency is enhanced
by the optical communication lens 45 and the optical element module
22.
[0081] The invention may be modified in various ways without
departing from the scope and spirit thereof.
* * * * *